Conventional fluorescent tubes (low-pressure discharge lamps, for example the models T5 and T8) by their nature emit generated light in all directions around the longitudinal axis of the tube. Because retrofit tube lamps in LED technology have LEDs arranged in a line, these lamps generally have a limited emission angle which is determined by the emission characteristic of the LEDs.
In order to enable a targeted emission of the light depending upon the application, there are retrofit LED tube lamps in which the lamp bases (also referred to as end caps) are configured rotatably relative to the tube bulb, in which the light engine, i.e. the arrangement of the LEDs on a substrate which holds the LEDs, mechanically and simultaneously enables the supply of electrical power to the LEDs. An electronic driver (also referred to below simply as a driver) is usually used, which provides an appropriate power supply for the LEDs from the available mains voltage. In this case it must be ensured that there is a secure electrical connection of the connecting pins in the end caps to the driver, since the mains voltage is still available at this point. Moreover, the torque occurring during installation of the lamp into a socket must be absorbed by the rotary mechanism.
For this purpose, a latching mechanism, which enables the end cap to turn in relation to the tube bulb in defined angular steps, is usually used in the lamp bases. In this case the part of the end cap with the connecting pins is pulled out against a spring, rotated and, after release, is latched again due to the spring action. Such a mechanism has a space requirement of approximately 10 mm, so that the part of the lamp illuminated by the LEDs is reduced in size.
The driver is connected to the connecting pins by means of cables. This connection is loaded in particular by frequent turning. Loosening of or damage to this connection can constitute a safety risk due to the applied mains voltage.